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The King Oyster

(Pleurotus eryngii)

King Oyster mushrooms, also commonly know as King Trumpets, are delicious, meaty culinary mushrooms. However, these beauties are a little more finicky to grow than their oyster mushrooms cousins (Blue, Pearl, Yellow, Garden) as they are more sensitive to temperature and humidity.

The Mushroom Grow Kit is intended to be grown inside. The Kit contains a bag of hardwood sawdust inoculated with King Oyster mycelium and is ready to ‘fruit’ straight from the bag.

Download PDF instructions here.

Step 3c


Step 1: Inspect your Mushroom Grow Kit

  • Examine your bag to make sure it is fully myceliated (white all over). If so, then it is ready to start fruiting! However, if you can see areas of brown sawdust that are not myceliated then place your kit in a dark location (~18-24 C), and check it every day until it is all white.
Step 2: Choose a location for your kit

  • King Oysters like it cool and humid so choose a location that ranges between ~15-18 C, is bright but not in direct sunlight and is the most humid part of your house.
Step 3: Prepare for fruiting

  • Keep the bag closed and watch for the development of tiny baby mushrooms (primordial/pins).
  • Once ‘pinning’ begins, start cutting around the bag 1-2 inches above the baby mushrooms and remove the top part of the bag.
  • Next, make a ‘Humidity Tent’ to go over your Grow Kit to help create a humid environment for your mushrooms to grow. Get a clear plastic bag (so light can come through) that is large enough to loosely cover the grow kit with enough room for the mushrooms to grow. Cut approximately 10-1.5cm holes to allow for air exchange (CO2 out O2 in) and place it over your grow it.
Step 2
Step 2b
Step 4: Care for your mushrooms

  • Lift up & replace the ‘Humidity Tent’ 2 to 5 times a day to spray the inside of the tent with water and allow for fresh air in.
  • If your mushrooms start to grow long and stringy, it is usually a sign that there is too much C02 so ventilate the mushrooms more often and/or increase the number or size of holes in the bag. If your mushrooms are drying out, increase the humidity by spritzing more often.
Step 5: Harvest, Storage and Cooking

  • King Oyster mushrooms can grow quickly and be ready to harvest between 4 to 7 days after pinning.
  • Harvest your mushrooms before the caps flatten out and become concave by cutting each mushroom at the base with a knife.
  • It is best to cook your mushrooms when they are fresh but they can be stored in the fridge for about a week in a paper bag (not plastic!)
  • The stems of king oysters is what they are prized for as they are thick and meaty texture but the caps are equally as good. Many people use them to replace Portobello mushrooms in recipes or even grill them like scallops or meat.
Step 6. Compost your ‘spent’ Grow Kit:

  • Once you are done fruiting your kit, break up the sawdust/mycelium and put it in your home or city compost or use as a soil amendment in your garden bed.

  • Mushrooms produce airborne spores as they grow. When released from the gills they produce a dusty surface on your grow kit and surrounding area. To reduce exposure fruit your kit in a well ventilated area, use a ‘Humidity Tent’ and harvest mushrooms while they are still young.
  • Always cook mushrooms before consuming.

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